Sewing machine with differential feed

ABSTRACT

The invention is concerned with a sewing machine with differential feed means for maintaining the surplus width of garment blanks and simultaneously fixing the surplus width maintained by a seam in which the difference of the amount of feed of the feed dogs is controlled by a rotating program carrier, with a measuring wheel as an impulse emitter that scans the actual material feed at the stitch forming location and controls a step motor that drives the program carrier.

United States Patent [191 Dobner et al.

- 1 SEWING MACHINE WITH DIFFERENTIAL FEED [75] Inventors: ReinholdDobner, Kaiserslautern;

Erich Willenbacher, Karlsruhe; Wolfgang Baus, Kaiserslautern, all ofGermany [73] Assignee: Ptaff Industriemaschinen GmbH,

Kaiserslautern/Pfalz, Germany [22] Filed: Dec. 8, 1972 [21] Appl. No.:313,515

[30] Foreign Application Priority Data Dec. 10, 1971 Germany 2161295[52] US. Cl. 112/209 [51] Int. Cl D051) 27/08 [58] Field of Search..112/2, 79, 121.11, 121.12, 1l2/121.13, 136, 203, 205, 208, 209, 211,212

[451 May 7,1974

[56] References Cited UNlTED STATES PATENTS 3,174,449 3/1965 Bono112/209 3,368,507 2/1968 Orth 112/209 3,611,817 10/1971 Smith 112/209 XPrimary Examiner--Werner H. Schroeder Attorney, Agent, or FirmRobert H.Jacob I ABSTRACT The invention is concerned with a sewing machine withdifferential feed means for maintaining the surplus width of garmentblanks and simultaneously fixing the surplus width maintained by a seamin which the difference of the amount of feed of the feed dogs iscontrolled bya rotating program carrier, with a measuring wheel as animpulse emitter that scans the actual material feed at the stitchforming location and controls a step motor that drives the programcarrier.

3 Claims, 4 Drawing Figures PATENTEDMAY Y 1914 SHEET 3 OF 3 Fig.4

(I al The invention relates to sewing machines of the type equipped withdifferential feed means for maintaining the surplus width on cut blanksof clothing and for simultaneously fixing of the maintained width bymeans of a seam, where the difference between the amount of feed of thefeed dogs is controlled by a rotating program carrier. A machine of thistype serves, for example, for fitting in the surplus width of sleeveblanks in order to produce automatically the differences required in thegathering of the arm joint in the individual circumferential sections ofthe sleeve.

In a known machine of this type (German Pat. No. 1,760,182) the programcarrier consists of a cam disk which, in order to effect its controlledrotary movement, is coupled to the arm shaft of the machine by Way of areduction gear. Thus, a complete rotation of the program carrier isattained upon termination of a predetermined number of stitches. As aresult the seam program stored on the cam disk can only be carried outwith a stitch length setting coordinated to this seam length.

The feed elements however, influence the feed of the materialsdifferently for different kinds of materials and depend also on theinstant feeding speed as to their reaction to the transportingconditions. Besides, the gathering of the feeding elements is stronglyinfluenced by the characteristics of the material to be sewn and variesespecially in cases of deflections between the direction of feed and thedirection of the threads of the textile material. The amounts ofdifferences thus developing between the desired value and the actualvalue of the feed path per stitch add themselves so strongly for anumber of stitches required of the gathering program provided on theprogram carrier that even sewing results are out of the question.

For that reason the automatic control of the gathering effect by theseamstress can be manually influenced with the known machine initiallymentioned in order to compensate for deviations from the regular sewingprogram.

The adjusting of the known machine to different lengths of seams as itis required for executing different model sizes furthermore involvesconsiderable difficulties with the previously known machine. A change ofthe seam length at which the given program is to be executed requires acorresponding adaptation of the basic stitch length of the machine, ameasure therefore which for the reasons mentioned is very time consumingand inaccurate.

These insufficiencies are to be eliminated in accordance with theinvention and an arrangement is to be provided which automaticallycompensates itself from the characteristics of the feeding faults causedby the material to be operated on. For this purpose it was necessary tosolve the problem to control the operation of the program carrier foreffecting the change of the gathering effect of the feed members by ascanning element influenced by the effective work blank feed. Inaccordance with the invention this problem is solved in that a measuringwheel scanning the actual material feed at the stitch forming locationcontrols a step motor as impulse emitter which drives the programcarrier. Depending on the existing requirements it is possible in thisconnection to scan the non-gathered material being sewn which is fed tothe stitch forming location or the material already gathered behind thestitch forming location, while the impulse emission of the impulseemitter is adapted to the changed conditions.

Suitably the measuring wheel is arranged in the proximity of thematerial feed dog in order to scan the material directly. Thepossibility exists, however, to determine the actual material feed by ameasuring wheel arranged remotely from the stitch forming location. Inthat case the measuring'wheel measures, for example, the consumption ofa non-stretchable material band that has to be sewn along.

In order to adapt the gathering program of the program carrierautomatically to seam lengths selectable at random an adaptable impulsecounter is provided between the impulse emitter and the stepping motor,which further switches the stepping motor when it is set back by way ofan onward switching impulse.

A particularly fine grading step of the seam length adjustment isobtained in that the machine is provided with switching means where theimpulse emitter releases the opening of the counting operation of theimpulse counter, as well as that of a second impulse counter by way of abi-stable storage unit whose received counts are connected to a secondimpulse emitter which produces impulses of very high constant frequencyand the second impulse counter when set back to its initial positionupon reaching a predetermined counter position closes by way of thestorage unit the counting functions of both impulse counters.

An embodiment of the invention is illustrated in the accompanyingdrawing in connection with a sewing machine in accordance with theinvention and in which:

FIG. 1 is a schematic illustration of one embodiment of a sewing machinewith its prime mover,

FIG. 2 is a graphic illustration of the feed mechanism of the sewingmachine,

FIG. 3 is a side view of the stitch forming toolsof the sewing machine,and 9 FIG. 4 is a simplified circuit of the electrical controls.

FIG. 1 shows the housing 1 of a sewing machine which is driven by thedrive motor 3 by way of a V-belt 2, the number of rotations of which canbe controlled by a foot pedal 4 by way of an actuating lever 5 of motor3.

The sewing machine has, a main feed dog 6 (FIG. 2) and a lower auxiliaryfeed dog 7, each of which is carried by a support 8 and 9, respectively.These supports present bifurcated ends 10, 11 into which extendeccentrics l3, 14 mounted on a shaft 12. Shaft 12 is driven in aconventional manner, not illustrated, in order to impart liftingmovements to feed dogs 6 and 7.

Disposed parallel to and in driving connection with therebetween. Theinner shaft 21 projects from the shaft 20. A bifurcated lever 22 isrigidly connected with the shaft 20 and has linked to it the support 8which is connected with the main feed dog 6. A bifurcated lever 23 isrigidly connected with shaft 21 and the support 9 housing 1.

I I 3 to which the auxiliary feed dog 7 is connected is linked to saidlever 23.

The free end of the eccentric bar 18 is linked to a bolt 24 which isconnected rigidly with a guide member 25 and rotatably with a guideelement 26. The guide element 26 is linked by means of a stud 27 to alever arm 28 which is secured by means of its hub to the shaft 20, whilethe guide member 25 is rotatably linked by means of a stud 29 to a lever30 that is secured to a setting shaft 31.

The free end of the eccentric bar 19 is linked to a rod 32, which isrigidly connected with a guide element 33 and is rotatably connectedwith a guide member 34. Guide member 34 is linked by means of a stud 35to a lever 36 which has a hub secured to a rod 21, while the guideelement 33 is turnably connected by means of a pin 37 with a lever 38that is secured to a setting shaft 39. As shown in FIG. 2, levers 30 and38 as well as guide elements or members 25, 26, 33 and 34 are of thesame effective length.

' A lever arm 40 is mounted on setting shaft 31 which is connected to anarm of a lever 42 by way of a link bar 41. The other arm of the lever 42mounted on shaft 43 which is journalled in the housing of the sewingmachine presents a spherical head which is guided in a slot 45 of asetting disk 46 that is likewise rotatably mountedin housing 1. The slot45 extends spirally to the axis of rotation of the setting disk 46 insuch a manner that the main material feed dog 6 may be set for file of aprogram support that is in the form of a control disk 55. The controldisk is seated on the drive shaft 56' (FIG. 1) of a stepping motor 57mounted on the A lever 58 is clamped on the setting shaft 39 andconnected by a link bar 59 to a leverarm 60 which is secured to asetting shaft 61 journalled in housing 1. A bridge 62 is mounted onsetting shaft 61 between the arms of which a further bridge member 63 isrotatably journalled by means of studs 64. The arms of the bridge member63 are connected by a bolt 65 to which an ec- --arm 73 is connected withthe other end of the rocking shaft 72 which is connected by way of alink member 74 to'an arm of a double armed lever 75 journalled likewisein housing 1. The other arm of lever 75 engages an arm 76 (H6. 3) of anupper auxiliary feed dog 77 which is in the form of a double armedlever. The auxiliary feed dog 77 is supported by a guide bar 78 which islinked to support member 79 that is secured to the lower end of apresser foot bar 80 of known form of construction. The presser foot baris guided in a bearing sleeve 81 journalled in housing 1. in addition apresser foot 82 is secured to the support member 79 which is equippedwith a sole'83 that cooperates with the feed dogs 6 and 7thathasrecesses 84 for the passage of toes of the auxiliary feed dog 77that engage the material being sewn.

A bar 86 is disposed in the hollow presser foot bar 80 andis provided atits lower end with a roller 88 that is guided in a bifurcated part 87 ofthe upper feed dog 77 and which is moved axially up and down in a known.manner for effecting the thrust movements of the auxiliary upper feeddog 77.

A crank 89 secured to arm shaft 67 (FIG. 2) is in op- 1 erativeconnection by way of a link bar 90 with a needle bar 93 equipped with aneedle 91 and journalled in a guide member 92.

The needle 91 (FIG. 3) here works in a known manner with a looper (notillustrated) driven below the stitch plate 94 through a stitch hole 95.One each slot 96 and 97 are provided in the stitch plate 94 ahead of andbehind the stitch hole for the passage of the feed dogs 6 and 7. v

The feed dogs 6, 7 and 77 are arranged in a manner that the main feeddog 6 can make contact with the sole 83 of the feed dog 82 behind thestitch hole 95 As seen in the direction of sewing and thetwo feed dogs 7and 77 ahead of the stitch hole 95. V

The control of the step motor 57 is by way of a control circuit with apulse emitter, known per se, in the form of a pole wheel 98. For thispurpose a support 99 is secured to the bearing sleeve 81 for the presserfoot bar 80 which carries a downwardly extending stud 101 on a lateralchuck 100. On this stud a sleeve 102 is slidably mounted which ispressed by a spring 103 provided between it and chuck againsta safetydisk 104 fastened to the lower end of stud 101. Sleeve 102 is providedwith an arm 105' which has rotatably secured to it a bearing member 106in which the pole wheel 98 is rotatably mounted.

With the presser bar 80 in downward position the pole wheel 98 biasedbyspring 103 rests on the material being sewn laterally of the frontpart of the sole 83 of the presser foot 82. In order to achieve raisingof the pole wheel 98 together with the presser foot 82, an arm 107extending laterally from the sleeve 102 is provided which reaches beyondthe support 79 and is carried along by it as the presser bar 80 israised. y

The pole wheel 98 which is symbolically illustrated in FIG. 4 isprovided in a known manner with a pair of Hall generators that havecoordinated therewith a number of permanent magnets. As the pole wheel98 rotates the two Hall generators are penetrated by varying magneticfields and generate alternating potentials whose frequencyisproportional to the speed of rotation of the pole wheel 98. Thealternating potential is fed to an impulse dressing stage 108 which isarranged in a manner that an impulse appears at the output of theimpulse dressing stage for each millimeter of the length of the pathcovered by the pole wheel 98. This impulse is conducted to the settingentrance of a bistable storage unit 109 whose output A is connected byway of a reversing element 110 with the closing entrance of an impulsecounter 111 and whose output is connected with the closing as well asalso with the back setting entrance of a second impulse counter 112. Theoutlet of the counter 111 is connected by way of a reversing element 113with the resetting entrance of the counter 111 as well as also with aswitching amplifier 114 for the stepping motor 57. At the countingentrances of the two impulse counters 111 and 112 an impulse emitter 115is connected which constantly emits impulses of a very high frequency,for example, 33 kc. The output of the impulse counter 1 12 is connectedby way of a reversing element 1 16 and or-member 117 to the resettingentrance of the storage unit 109. A second entrance of the or-member 117is connected with the output? of a bi-stable storage element 118 whosesetting entrance is connected by way of a switch 119 connected with thefoot pedal actuating plate 4 for the drive motor 3, to the plus pole ofa source of potential. The resetting entrance of the storage element 118 is connected by means of a reversing element 120 with a slotinitiator 121 which cooperates with a flag 122 secured to the controldisk 55 (FIG. 1) and rotating therewith.

At the outputxof the storage element 118 (FIG. 4) there is alsoconnected a relay 123 whose rest contacts 124 are located in the circuitof the drive motor 3.

The counter 111 is adjustable by means of a preselecting keyboard 125(FIG. 1) which is provided in a control box 126 mounted in the operatingrange of the seamstress on the sewing machine which accommodates theentire switching means. The counter 112 on the other hand is set to afixed counting value.

The arrangement operates as follows:

The basic setting of the feeding magnitude of the feed dogs 6, 7 and 77(FIG. 2) takes place in common by turning the setting disk 46 wherebythe spiral shaped nut 44 turns the setting shaft 31 by way of the lever42 connected therewith by means of a joint.

The setting shaft 31 when turning carries along the lever 30 and thussets the stud 29 serving as the axis of rotation for the link or guidemember 25 in relation to the stud 27. During the rocking movement of thebolt 24 through eccentric bar 18 the link member 25 therefore executes apure rotary movement about the stud 29, whereas the link member 26executes besides this rotary movement also a relative movement about theshaft 20. This relative movement is transmitted by the lever 28 as arocking movement onto the lever 22,

which imparts thrust movements in the direction of feed to the main feeddog 6 by way of support 8. The magnitude of the feed movement depends onthe position of the setting screw 46 and thus on the magnitude of thesetting difi'erence between the studs 27 and 29.

The turning of the setting shaft 31 simultaneously effects a rotating ofthe setting shaft 39 by way of the lever arm 47, links 49 and 50 andlever arm 48. The lever 38 that is fixedly connected with the latterthereby moves the link 33 so that the stud 37 is displaced relative tothe stud 35. During the swinging movement of the bolt 32 through theeccentric bar 19 therefore the link 34 efiects for reasons stated inconnection with the function of parts 24 to 30 besides a rotary movementabout the stud 37 a relative movement about the shaft 21. This movementeffects a rocking movement of the shaft 21 which imparts feed movementsto the auxiliary feed dog 7 by way of lever 23 and support 9.

Furthermore, lever 58 effects during the turning of the setting shaft 39a rotating of the setting shaft 61 by way of the link 59 and lever arm60. The strut 62 which is securely fastened thereto turns the strut 63so that the studs 64 serving as the axis of rotation for the strut 63are displaced relative to the stud 70. During the swinging movement ofthe bolt 65 by the eccentric bar 66 the strut 63 carried out a purerotary movement about the stud 64 in a manner similar to the settingarrangement described above, the link 69 however also effects a relativemovement about the rocking shaft 72 and thus causes the same to effect arocking movement by way of lever arm 71. These rocking movements aretransferred by the rocking shaft 72 by way of lever arm 73, link 74 andlever 75 (FIG. 3) to the upper auxiliary material feed dog 77 as feedmovements.

The setting disk 46 thus adjusts the stitch length of the main feed dog6 as well as also that of the two auxiliary feed dogs 7 and 77 thatengage the work blank in the manner of tongs. To the amount of feed ofthe two auxiliary feed dogs 7 and 77 that supply the material to thestitch forming location there is in addition superimposed an amount offeed which depends on the profile of the cam disk 55.

During the sewing operation the material is displaced by the twoauxiliary feed dogs 7 and 77 by a larger amount than by the main feeddog 6 from which the required gathering results or the adherence to thesurplus width in a manner known per se.

Prior to starting thesewing the step motor 57 and therefore also thecontrol disk 55 are in their starting position in which the flag 122extends into the slot initiator. The two bi-stable storage units 109 and118 are set back. The impulse emitter swings steadily and impartsimpulses to the counting receipts of the two impulse counters 111 and112. However these impulses are not counted because a locking signal ispresent from the storing unit 109 at the locking entrances of thecounters 111 and 112. Both counters 111 and 112 are positioned at zero.

By the seamstresss moving the foot pedal plate 4 backwards theswitch 119 is closed and the storage unit 118 is set so that the relay 123 dropsand the rest contacts 124 in the circuit of the motor remain closed.Simultaneously the storage unit 109 is freed which previously wascontinuously set back by way of the or member 117 through the storageunit 118. Now the seamstress can start the sewing operation by steppingon the foot pedal plate 4 in which connection she can control the sewingspeed in a known manner by; means of the foot pedal 4.

During the sewing operation the pole wheel 98 is turned by the movingmaterial being sewn. The alternating potential produced by the two Hallgenerators is supplied to the impulse preparation stage 108 and isutilized there in a manner that for each millimeter of material fed animpulse appears in its output. This impulse sets the storage unit 109.As a result the latches at the counters 111 and 112 are released so thatthe impulses supplied by the impulse emitter 115 are now countedsimultaneously in both counters 111 and 112.

If now the counter 112 is set to a constant numerical value, forexample, 7, then the seventh arriving impulse of the impulse emitter 115produces at its exit a zero signal which is inverted at the reversingstage 116 and sets back the bi-stable storage unit 109 by way of theor-element 117. As a result, both counters 111 and 112 are closed andcounter 112 is simultaneously returned to zero. The counter position 7is maintained in counter 1 11.

The next impulse at the impulse maker 108 releases v in the same mannerby way of storage unit 109 the freeing of both impulse counters 111 and1 12, the counting of seven impulses into both counters and the returnof the storage unit 109, whereupon the counter position of the impulsecounter 11 1 stands at 14.

This manner of operation continues until the counter 111 has reached acounter position which is identical with the selected counter positionat the control box 126. At that moment the counter 111 emits a zerosignal which appears at the output of the reversing stage 113 as anL-signal which sets back the counter 111 to zero and simultaneouslyswitches the stepping motor 57 by way of the switching amplifier 114.

The next impulses of the path are again multiplied by seven count thecounter 1 1 1 up to preselection and release further steps of thestepping motor 57. This motor rotates dependent on the number of thearising impulses and the preselected choice set up in the control box126.

During its rotary movement by means of the stepping motor 57 inaccordance with the material feed, the control disk 55 rocks thedouble-lever 53 which acts on the two links 49 and 50 by way of thetransfer bar 52. With constant turning position of the setting shaft 31the rotational position of the setting shaft 39 is thereby changed as aresult of which also the magnitude of the feed device of the twoauxiliary feed dogs 7 and 77 which effect a common feed movement changeswith respect to the feed movement of the main feed dog.

The formation of the contour of the control disk 55 is determined by thedifferential displacement of the auxiliary feed dogs 7 and 77 during acomplete course of a scam in relation to the main feed dog 6, while theangular rotation of the control disk 55 corresponds exactly to theadvance of the material being sewn. Thus, while gathering the surpluswidth on sleeve blanks of garments entirely identical shapes of fit canbe obtained. The different seam lengths caused by the different sizes ofsleeves can be so set by adjustment of the preselecting keyboard 125 onthe control. box 126 that the controldisk 55 effects a complete turncorresponding to the lengths of seams now changed for performing theentire seam course. in this manner the gathering program stored on thecam disk can be adapted to the most variegated lengths of seams whichare: smaller than a predetermined maximum seal length to be made. Whenthis maximum adjustable seam length in the preselection 100 at thepreselecting keyboard 125 amounts, for example, to 68 millimeters, thena desired seam length L can be produced by setting to the preselection xL X 100/680.

At the end of the seam the control disk 55 has rotated through 360 andthe flat rotating with it enters the slot initiator 121. This initiatorsetsback the storage unit 118 by way of the reversing element 120.Thereby the storage element or memory 109 is closed and the furtherimpulses from the pole wheel 98 are faded out; the cam disk 55 remainsin this end position. ln addition the relay 123 opens the rest contacts124 which renders the drive motor 3 devoid of current. The sewingmachine stops and indicates to the seamstress the end of the operation.

The course of the work can, of course, be changed without changing thebasic principles of the invention; thus for example an arrangement maybe provided by means of which the direction of rotation of the steppingmotor 57 and thereby of the control disk. 55 can be reversed in order toenable the sewing of right or left arm lengths. Besides the starting andthe end of the sewing operation can be controlled by means of photocells in order to insure that the sewing machine runs only so long asthere is material under the needle 91.

We claim:

1. Sewing machine having differential feed means for maintaining surpluswidth of garment blanks and simultaneously fixing by a scam the surpluswidth maintained, where the difference of the amount of feed of the feeddogs is controlled by a rotating program carrier comprising a measuringwheel which scans the actual amount of material feed at the stitchforming location of .the machine, said measuring wheel having at leastone impulse emitter controlling a stepping motor, said program carrierbeing driven by said stepping motor.

2. Sewing machine in accordance with claim 1, including an adjustableimpulse counter between said impulse emitter and said stepping motor,said impulse counter being adapted to be set back, thereby imparting aforward switching impulse to said stepping motor.

3. Sewing machine in accordance with claim 2, including a bi-stablestorage unit, a second impulse emitter and a second impulse counter,said first impulse emitter being operative to release the countingfunctions of said first and said second impulse counters by way of saidbi-stable storage unit, the counted inputs of said first and said secondimpulse emitters being connected with said second impulse emitter whichis oper-v ative' to produce impulses of very high constant frequency,and said second impulse counter being operative upon resetting to itsstarting position after having attained a predetermined position ofcount to stop the counting functions of both impulse counters by way ofsaid storage unit.

1. Sewing machine having differential feed means for maintaining surpluswidth of garment blanks and simultaneously fixing by a seam the surpluswidth maintained, where the difference of the amount of feed of the feeddogs is controlled by a rotating program carrier comprising a measuringwheel which scans the actual amount of material feed at the stitchforming location of the machine, said measuring wheel having at leastone impulse emitter controlling a stepping motor, said program carrierbeing driven by said stepping motor.
 2. Sewing machine in accordancewith claim 1, including an adjustable impulse counter between saidimpulse emitter and said stepping motor, said impulse counter beingadapted to be set back, thereby imparting a forward switching impulse tosaid stepping motor.
 3. Sewing machine in accordance with claim 2,including a bi-stable storage unit, a second impulse emitter and asecond impulse counter, said first impulse emitter being operative torelease the counting functions of said first and said second impulsecounters by way of said bi-stable storage unit, the counted inputs ofsaid first and said second impulse emitters being connected with saidsecond impulse emitter which is operative to produce impulses of veryhigh constant frequency, and said second impulse counter being operativeupon resetting to its starting position after having attained apredetermined position of count to stop the counting functions of bothimpulse counters by way of said storage unit.